Automatic Monitoring of the Electric Fleet

In this column, I have often emphasized the advantages to automating the battery charging process by retrofitting older timer-controlled chargers with the latest microprocessor (computer) controls.

Such an upgrade maximizes usable battery capacity and cycle life while minimizing electrical utility costs. Many new chargers on the market today incorporate sophisticated auto controls, and some go the next logical step by offering a computer communication option. Tying the built-in charger computers together with a central computer is potentially very important to large electric fleet operators for several reasons:

  • Reduces downtime due to unexpected battery problems

  • Minimizes electric utility costs

  • Provides information important to proper sizing of battery fleet

  • Facilitates properly scheduled purchases of new batteries

  • Results in improved battery handling (swapping) schedules

  • Cuts man-hours associated with battery monitoring and record keeping

It is possible to keep tabs on a battery fleet from a remote central location because charger microprocessors can be programmed to communicate significant battery condition information to a monitoring office computer. A charger’s microprocessor control should be able to compare the battery’s dv/dt curve (change in voltage over time) to specifications stored in memory, and report any deviations to the central computer to schedule battery maintenance. Catastrophic battery failure that disables a critical lift truck in the middle of a shift need not happen. By knowing that a battery is in decline, backup can be planned, and an orderly maintenance schedule can be followed. Catching a problem early also provides a better chance of getting service while the battery is still under the best terms of its warranty. Batteries usually give generous warning that problems are on the way, and these signs, in times past, were usually read by the battery room supervisor– position that is seldom staffed under today’s low-overhead philosophy. Downtime due to improper charging practices can also be reduced by monitoring. Industrial deep-cycle batteries work best and live the longest when the battery is brought back to the charger for a full 8-hr charge when it is 80% discharged. Repeated deviation from this protocol increases battery life-cycle costs through overcharging and unnecessary handling. Conversely, if batteries are randomly pulled off of chargers before the 8-hr cycle is complete, production will suffer unnecessary "dead battery" downtime incidents- and, without monitoring, the root cause of this downtime might be difficult to determine. Monitoring concepts have been developed that allow tracking of individual batteries even though these batteries may be plugged into any of several different chargers, and regularly swapped out between a number of active lift trucks. One approach is to equip each battery’s connector with an I.D. microchip that provides the battery’s data to the central computer each time it is brought back to a charger. Carrying this idea further, an I.D. chip could also report the number of the lift truck the battery has just completed its shift in, providing valuable workload data for scheduling. The amount of electricity it takes to recharge a battery can be part of the central record, as well as time between visits to the charger. Batteries that require increasingly frequent charging, while workload remains constant, are the ones flagged for maintenance attention under this type of system. Anyone facing the large capital expenditures involved in purchasing new batteries for a large fleet would appreciate the information a central computer monitoring program could provide. Once the performance history of various battery capacities in a plant’s unique operations are a matter of record, it becomes clear just how much battery capacity is needed to complete a shift. Such knowledge puts the battery purchaser in the best possible position to make wise, economical battery buys. When a large bank of chargers is used for simultaneous charging of batteries overnight, central computer control can provide utility bill savings by spreading out the load– staggering the turn-on times of chargers to reduce peak electrical demand. Central control can also be programmed to refuse to boost-charge batteries during mid-day break periods, and thereby enforce proper charging protocol.

A Fleet Monitor Wish List

What would you like to know, need to know, to plan the best possible electric fleet operation? Let’s recap:

  • How well are the batteries and trucks matched to the workload– can they do a full shift on a single 8-hr charge? Is there excess capacity?

  • Operators adhering to proper charging protocol?

  • Which batteries are showing signs of diminished capacity and need maintenance attention?

  • What are the best batteries, capacity and brand name, to buy for my operation? How can I best schedule major battery purchases in advance?

In many ways a central automated record keeping system can help provide answers for these questions. Watch upcoming Battery Tech columns for more specifics on what is now available from major battery charger manufacturers.

For more information, contact Arcon Equipment Inc. (440) 232-1422.